Water and wastewater treatment system and process for contaminant removal

ABSTRACT

A system and process for removing contaminants from water and wastewater, where the water or wastewater is transformed into purified water that can be discharged to the environment. Wastewater is transported through several stations for purification, including an electrochemical cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of application Ser. No.09/494,219, filed Jan. 28, 2000, which is incorporated fully herein byreference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to the field of water andwastewater treatment systems, and more particularly to systems utilizingan electrochemical cell to facilitate flocculation of particles in thewater or wastewater to permit the discharge of treated wastewater to theenvironment or purification of potable water.

BACKGROUND OF THE INVENTION

[0003] Contamination occurring in aqueous-based solutions has become aserious concern to society. In particular, problems associated with thedisposal of industrial wastewater have been mounting. Disposing of thewastewater is not only very expensive and time consuming, but alsoextremely harmful to the environment. Some areas of concern in thedisposal of wastewater, which are particularly suited to treatment usingthe subject system, are:

[0004] a. Removal of emulsified oils, both petroleum hydrocarbons andfood base oils.

[0005] b. Partially dissolved contaminants which add to turbidity andcolor of water.

[0006] c. Negatively charged metals such as arsenic, molybdenum, andchromium.

[0007] d. Positively charged heavy metals such as copper, cadmium,nickel, lead, and zinc.

[0008] e. Contaminants such as ammonia, mercury, arsenic and iron whichreact with oxygen.

[0009] f. Contaminants which react with aluminum or iron such aschlorinated organics.

[0010] g. Poorly settling TSS (total suspended solids) such as silt,ink, wood extractives, clay and microorganisms.

[0011] One example of a particular contaminant of concern is petroleumhydrocarbon contaminants in shipyard wastewater, including the oilywastewater resulting from cleaning out ship bilges and fuel tanks. Theprimary concern with this wastewater is finding an effective method forits disposal. While various methods have been developed to deal withthis oily waste, none have been entirely successful given the extremelyvaried nature and content of the contaminants in the water, with oilcontent ranging anywhere from 0.5% to 50% in volume. Included among themethods attempting to control these waste streams are a wide variety ofchemical and physical procedures.

[0012] Chemical procedures have attempted to cause a predeterminedreaction between chemical additives and impurities contained within thewaste stream. The most common reactions are designed to cause theimpurities and the chemical additives to coagulate, wherein theparticles increase in size and then separate by either floating on orsettling below the treated water. The most popular chemical utilized isalum, which when added to the wastewater, separates much of the wasteout of the water. There are several problems with chemical coagulationin general, including the generation of very large quantities ofresiduals that need to be disposed of and imprecision because the amountof chemical necessary for a given volume must always be estimated due tothe varying nature of the waste streams.

[0013] Physical procedures are designed to achieve similar results aschemical additive procedures, but to a lesser degree of purity in thefinal aqueous solution. Filters, centrifuges, plate separators, andclarifiers are the most common physical procedures employed to removecontaminants from aqueous solutions. In most cases, the impurities thatare removed physically are suspended solids or poorly emulsifiedcontaminants.

[0014] While the chemical and physical procedures of treating wastestreams were thought to be adequate at one time, the results of disposalof solutions treated in this manner have been disastrous. Oceans,streams, lakes and underground wells have all fallen victim to thecontamination resulting from the impurities that were not removed bythese methods. In fact, because of the dumping of contaminatedsolutions, many rivers and streams are considered waste sites and entirelakes have been drained so that the lakebeds can be hauled away to betreated as hazardous waste. The main problem is that regardless ofwhether chemical procedures, physical procedures, or a combination ofthe two are utilized, the content of impurities in the wastewaterremains in an unacceptable range.

[0015] While it was known that the purification of waste streams, and inparticular the coagulation of contaminants without the addition ofchemicals, could be accomplished through electrolytic treatment in aprocess called electrocoagulation, the wide range of contaminants,varying contaminant concentrations and large and variable volumes ofwastewater in the industrial waste streams generally discouraged itsuse. However, patents directed to electrolytic treatment apparatuses,methods and systems can be found dating back to the early part of thiscentury. Electrocoagulation is the process of de-stabilizing suspended,emulsified or dissolved contaminants in an aqueous medium by introducingan electrical current into the medium. Electrocoagulation generallytakes place inside a substantially sealed treatment chamber, where theimpurities are coagulated out of the aqueous medium.

[0016] Many other systems and cells have been disclosed and patented,each trying to convert contaminated water to purified water byseparating the contaminants from the water. Unfortunately, none of thesesystems have been able to solve the problems of variability, number andconcentration of contaminants associated with the treatment ofindustrial wastewater. These previous systems created large quantitiesof metal sludge and other contaminant sludge that added to the cost ofdisposal. Even systems that were able to overcome these problems hadother problems such as high labor cost (batch and dump methods); largeareas necessary for increased residence time, and high capital costs dueto electrical power and maintenance (on-line electrical systems); andlow efficiency (dilution with non-conductive materials). Other systemssuffered from design problems such as not accounting for the productionof generated gases or the build up of impurities onto the workingelectrodes, or creating an electrolytic cell that is too complex andwhich cannot be easily maintained.

[0017] Accordingly, there is a need for a wastewater treatment systemand process that removes contaminants, such as petroleum hydrocarbons,resulting in a product with impurities of considerably less than 15parts per million (PPM), that is cost effective, energy conscious, easyto use and easy to maintain.

BRIEF SUMMARY OF THE INVENTION

[0018] The present invention is directed to a treatment for water andwastewater and a process for removal of contaminants by utilizingchemical, mechanical, and electrolytic devices.

[0019] It is an object of this invention to provide a treatment systemand process of removal that removes impurities from water andwastewater.

[0020] It is also an object of this invention to provide a treatmentsystem and process of removal of contaminants from wastewater that iscost effective and energy efficient.

[0021] It is a farther object of this invention to provide a treatmentsystem and process of removal of contaminants from water and wastewaterthat is easy to use and easy to maintain.

[0022] In general, the subject invention has potential application totreat water and wastewater rather than using chemical methods such asinorganic cationic coagulants including the salts of aluminum (aluminumsulfate or “alum”, aluminum chloride, or poly aluminum chloride), iron(chlorides or sulfates), or calcium (chlorides or sulfates). Inaddition, sediments may be removed in the preparation of potable water.The subject invention may also be used as an aid to clarify waterfollowing biological treatment of wastewater.

[0023] A more complete understanding of the waste water treatment systemand process for the removal of contaminants will be afforded to thoseskilled in the art, as well as a realization of additional advantagesand objects thereof, by a consideration of the following detaileddescription of the preferred embodiments. Reference will be made to theappended sheets of drawings, which will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is flow chart of the wastewater treatment process of thepresent invention.

[0025]FIG. 2 is a side cross-sectional view of the electrochemical cellof the present invention.

[0026]FIG. 3 is an end sectional view of the electrochemical cell ofFIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The following detailed description illustrates the invention byway of example, not by way of limitation of the principles of theinvention. This description will clearly enable one skilled in the artto make and use the invention, and describes several embodiments,adaptations, variations, alternatives and uses of the invention,including what we presently believe is the best mode of carrying out theinvention.

[0028] The present invention satisfies the need for a water andwastewater treatment and contaminant removal process that is efficientand effective to purify water or to produce disposable water fromindustrial wastewater. This is accomplished by using a novel system andprocess of contaminant removal that includes an electrochemical cell forthe coagulation of organic and inorganic materials.

[0029] Referring now to the drawings, in which like reference numbersrepresent similar or identical structures throughout, FIG. 1 illustratesthe wastewater treatment process through the use of a simple flowdiagram. The wastewater, containing varying amounts of contaminants, isfed into a strainer 11 in step 10 to remove larger debris. In thisembodiment, which is exemplary of the system and process of the presentinvention, the contaminants consist primarily of petroleum hydrocarbonsthat are found, for example, in shipyard wastewater, including “bilgewater.” Other contaminants include larger debris that can be separatedout initially through the use of strainer 11. Following the initialstraining, the wastewater stream, free of the larger sized debris, issent to a classifier 13 in step 20.

[0030] The classifier 13 is a large tank with an inlet located in anintermediate area of the tank that receives the wastewater stream fromthe strainer 11. The wastewater stream is pumped into the classifier 13by means of a pump 302. A pump 304 is used to remove the wastewater fromthe classifier 13 and is located such that wastewater is pumped from thetop region of the classifier 13. This causes flow of the wastewater fromthe classifier inlet upwardly to the top region of the classifier 13where it is pumped out. Heavier particles in the incoming wastewaterstream settle downwardly in the classifier by force of gravity to cometo rest at the bottom of the classifier 13. An auger extends into thebottom of the classifier 13 to direct the heavy solids into a disposalcontainer 15. When the auger is activated, the solids at the bottom ofclassifier 13 are moved upwardly and out of the auger into the disposalcontainer 15 in step 24. The solids in the container 15 may be removedto a suitable solids disposal site such as a landfill.

[0031] The overlying liquid in the classifier 13 is pumped to asolid-liquid hydrocyclone 17 in step 22 by pump 304. The coarse solidsthat have not sunk to the bottom and that have entered the hydrocyclone17 with the overlying liquid are returned to the classifier 13 forfurther separation, while the wastewater stream is sent to feed tanks 19in step 30. The number and capacity of feed tanks 19 used in the systemis dependent on the amount of wastewater stream throughput. When morethan one feed tank 19 is necessary, they are aligned in a parallelconfiguration. Once in the feed tanks 19, the free oil in the wastewaterrises to the top in the first decant to be removed by a surface skimmer.The free oil from the skimmer then flows by gravity to the free oilstorage tank 21 in step 32 where it undergoes a second decant. The oilis pumped from the top of the free oil storage tank 21 in step 34 and isre-used for various applications. The wastewater underneath the oil(underflow) in the free oil storage tank 21 is returned to theclassifier 13 in step 36.

[0032] The wastewater in the feed tanks 19, underneath the oil remainingafter the first decant, is transported by pump 306 through an in-linebasket strainer 61 to an electrochemical cell 200 in step 40. Thewastewater is pumped to the bottom inlet 210 (FIG. 2) of theelectrochemical cell 200, which will be described in more detail inreference to FIGS. 2 and 3, below. Inside the electrochemical cell 200,the wastewater is passed over electrically charged plates arranged tocreate a serpentine path for the wastewater. In a process ofcoagulation, the negatively charged contaminants in the wastewater formclusters or “flocs” with the positively charged ions being released bythe charged plates. The clusters join with other clusters to form largerflocs that are easier to remove. In addition, the electrocoagulationprocess causes hydrolysis of the wastewater, releasing hydrogen gas andoxygen gas into the wastewater and forming hydroxyl ions. The oxygenacts to oxidize contaminants and the hydroxyl ions act to precipitatemetals out of the wastewater. This process of electrocoagulation will bedescribed in more detail below. The treated wastewater and gases exitfrom the top outlet 220 (FIG. 2) of the electrochemical cell 200 and aresent toward an in-line static mixer 23 in step 50. A portion of thewastewater that enters cell 200 is re-circulated through theelectrochemical cell 200 in step 42 by pump 308 at a rate sufficient toprovide turbulent mixing and scouring of the plates in cell 200. In thepreferred embodiment and as an example only, with a flow rate of 10gallons per minute to cell 200, a re-circulation flow rate of about 50gallons per minute to 100 gallons per minute is acceptable.

[0033] After exiting outlet 220, the wastewater is injected withcompressed air in step 52 and anionic polymer in step 54. The mixture isthen introduced into the in-line static mixer 23, which mixes thepolymer and air with the wastewater stream. Because the mixer is astatic mixer and because compressed air (or other suitable gas) is used,the amount of mechanical sheer on the polymer and coagulated solids fromcell 200 is limited, minimizing the breakup of the polymer and flocs. Atthe same time, the use of a static mixer with compressed air in thewastewater stream provides significant enhancement of the mixing ofpolymer with the wastewater stream. This enables the use of much loweramounts of polymer in the system generally, while still providingsignificant coagulation and separation of solids from the wastewaterstream. The compressed air mixed into the wastewater stream by thein-line static mixer 23 facilitates the contact of polymer with thecoagulated solids and creates flocs containing entrained gases. Thisresults in easier separation of the flocs from the wastewater in theflotation cell 27. The negatively charged polymer combining with thepositively charged flocs make larger diameter flocs with lower overalldensities, since larger sized flocs are more effective at accumulatinggas bubbles on their surfaces and in their void spaces. As a result, theoverall densities of the flocs are lower than the density of thewastewater, causing a portion of the flocs to rise to the surface andfloat. Later, when the gas bubbles escape from the floc, the overalldensity increases beyond that of the wastewater and a portion of theflocs sink.

[0034] The polymer and air can optionally be added to the wastewaterstream before the electrochemical cell 200. In that case, theintroduction of air promotes turbulence in the cell which promotescontact of the contaminants with the plates, thereby enhancingcoagulation, and the introduction of anionic polymer acts to scavengepositively charged contaminants, forming embryonic flocs, also enhancingcoagulation in the electrochemical cell 200. The addition of polymer andcompressed air prior to the electrochemical cell 200 is useful as wellwhere it is desired to remove positively charged ions from thewastewater. This procedure is described in more detail below withrespect to an alternative embodiment of the present invention.

[0035] The mixture of polymer, wastewater and air leaving the in-linestatic mixer 23 flows past a vertical pipe 25 in step 60. The verticalpipe 25 allows the majority of gases to vent in step 62 so that the riseof flocculated particles in the flotation cell 27 is not disrupted byexcessive turbulence due to escaping gases. After passing vertical pipe25, the wastewater flows into a flotation cell 27 in step 70. In theflotation cell 27, the entrained gases associated with the coagulatedsolids still remaining in the wastewater result in a decreased densityof the flocs, which is less than that of the wastewater, causing theflocs to rise to the surface of the wastewater in the flotation cell 27.The floating flocs flow over an overflow weir into a solids collectiontank 29 in step 72. The solids in the solids collection tank 29 arepumped to a filter press 31 in step 74 by pump 310. The filter press 31removes the water from the solids and returns the filtrate to theclassifier 13 in step 78. The solids are removed from the filter press31 after a pressure drop indicates that it is full. The solids arestored in a disposal container 38 in step 76 and may be removed to asuitable solids disposal site such as a landfill.

[0036] The underflow of the flotation cell 27, which is substantiallyfree of flocs, flows by gravity to a settling tank 33 in step 80. In thesettling tank 33, further separation of the coagulated solids can occurthrough gravity as the solids remaining in the underflow will generallyhave a density greater than the wastewater and will sink to the bottom.These solids are pumped to the filter press 31 in step 92 along with theflocs from the solids collection tank 29. The water, now substantiallyfree of solids, leaves the settling tank 33 over an overflow weir whereit enters into a polymeric filter feed tank 35 in step 90. This water ispumped to a plurality of in-line bag filters 37 in step 100 by pump 312,and finally to a polymeric filter 39 in step 110 where most of theresidual contaminants are removed. This final discharge of water withsubstantially reduced contaminants is released into the ground or sewerin step 120.

[0037] The primary advantage this process enjoys over chemical systemsis a significantly lower quantity of residuals for disposal, at lowercost and with better operational simplicity. The primary advantage ofthis process over physical systems is greatly improved contaminantremoval from the wastewater. The only contaminants that require disposalare the concentrated solids in the disposal containers.

[0038] Referring now to FIGS. 2 and 3, the electrochemical cell 200 isillustrated. In FIG. 2, a cross-sectional view of the electrochemicalcell 200 is shown as it would be viewed from the front of the device.The cell 200 is equipped with conductive plates 250 and 255 that arealternatingly connected to oppositely charged electrodes as will beexplained in more detail in reference to FIG. 3 below. The plates 250and 255 are evenly numbered so that there are an equal amount of anodeand cathode conductive plates. In order to provide easy replacement ofthe plates 250 and 255, they are installed into the cell 200 incartridge 257. The cell housing 205 has a removable cover 204 to allowthe interchanging of the cartridges 257. Further, the plates 250 and 255are large in area and few in number, which permits lower pressure andvoltage drops. The plates 250 and 255 are made of aluminum in thepreferred embodiment but may be composed of any one of a number ofmaterials based on the type of contaminants that are to be removed. Forexample, iron, platinum, carbon or titanium plates could be utilized.The plates 250 and 255 are separated by spacers 230 that are fabricatedfrom non-conductive material such as nylon to maintain a plate spacingthat in the preferred embodiment is approximately 0.5 inches. To achievea seal at the end of the cartridge 257 and thus create a serpentine flowpath, electrically insulated end plates 207 and 208 are used. The endplates 207 and 208 are held in compression against the cartridge 257 bymechanical means. The plates 250 and 255 are arranged in a manner thatcreates a serpentine flow path for the wastewater. This is done byleaving a gap between plates 250 and the end plate 207 on one end of thecartridge 257 and between plates 255 and the end plate 208 on theopposite end of the cartridge 257. The wastewater enters at the bottominlet 210 and is pumped through the cell 200 to the top outlet 220. Asthe wastewater winds its way through the cell 200, the electric fieldthat is generated when a voltage is applied to the plates 250 and 255causes the dissolved and suspended solids within the wastewater tocoagulate and form larger flocs. At the same time, gas bubbles aregenerated by the electrolysis of wastewater, causing the larger flocs tofloat. This entire process is referred to as electrocoagulation.

[0039] The most commonly used electrode plates are iron or aluminumbecause they give trivalent ions; most other cheap and easily accessiblemetals give only bivalent ions. Trivalent ions have a higher abilitythan bivalent ions to absorb onto particles in the wastewater becausethey have a higher charge density. In the preferred embodiment of thepresent invention, aluminum electrode plates are used.

[0040] The effectiveness of the release of the metal ions into thewastewater is crucial to the coagulation of the solids and to thecapability of the process in removing impurities. The release of metalions is dependent on several factors, including the amount of currentsent through the conductive plates, the residence time that thewastewater is in contact with the plates, and the level of turbulencecreated by the flow of wastewater through the system. In addition, therelease of metal ions must be balanced with the injection of polymer,with the goal being to run the lowest possible current but still releasesufficient levels of metal ions to initiate coagulation of thecontaminants in the wastewater. If the current is set a level that istoo high, excessive metal ions are released, thereby increasing theconsumption of the plates. When the consumption of the plates isincreased, additional polymer is required to coagulate the excess metalions, which increases the density of the flocs. Thus, it is important tofind a current that is high enough to release the metal ions from theplates, but low enough to maintain an acceptable floc density.

[0041] The key parameters in designing and operating the cell are platesurface area, wastewater flow rate and current. With a cell havingapproximately 20 square meters of total plate surface area and with aflow rate of 50 liters per minute, we have found that a suitable currentis in the range of 300 to 450 amperes. While the cell 200 has beenoperated using current less than 300 amperes and current exceeding 450amperes, the preferred range has produced the desired results. Priorsystems have had difficulty perfecting the residence time/turbulenceconditions, that is, being able to increase turbulence while maintainingadequate residence time of the wastewater within the electrochemicalcell. The present invention has solved this problem by introducing are-circulation stream at step 42 back into the bottom of theelectrochemical cell 200 which, in the preferred embodiment,re-introduces approximately 2 to 10 times the throughput rate of 10gallons/minute. The re-circulation stream creates high turbulence in thecell 200, scouring the conductive plates 250 and 255 so that the contactof wastewater with the plate surface is increased. This can be furtherenhanced, if required, by introducing compressed air into the wastewaterstream before it enters the cell 200.

[0042] The electrochemical cell 200 is constructed using stainless steelthat is internally vulcanized so that it is not conductive.Alternatively, rubber lined carbon steel or other materials orcomposites that provide structural strength without conductingelectricity could also be used. Wedges 242 are placed on both ends ofthe cell 200 in area 240, providing a seal at the ends of the plates toavoid bypassing of wastewater flow. The cell 200 also contains aremovable cover 204 to permit access to the inside of the cell and forcartridge replacement as explained above. The cover 204 is electricallyinsulated from the cartridge (250, 255 and 230) by a nonconductivegasket 206 and from the electrical headers 260 and 270 by anon-conductive fitting 209 that also provides a water tight seal.

[0043] The cell 200 is also unique in its ability to manage the gasbuild-up associated with the process. By directing the flow ofwastewater from the bottom 210 of the cell 200 to the top 220, asopposed to prior art, which directs the flow from side to side, there isno gas build-up and thus, no pockets of gas created to disrupt theprocess. The upward serpentine flow coupled with an outlet at the top ofthe cell allows gas to exit the cell without creating problems. Severalbenefits are realized by removing accumulated gases, including evenplate consumption, turbulent mixing, consistent gas flow, low voltagerequirements, and prevention of plate overheating.

[0044]FIG. 3 illustrates a partial side view of each of the electricalheaders. In FIG. 3A, a first electrical header 260 is shown. The bottomor first plate 250 is welded onto the first header 260 by weld 280, asis every odd numbered plate (counting from the bottom, 3, 5, 7, etc.).The second plate 255 is electrically insulated from the header withinsulation 290, as is every even numbered plate (2, 4, 6, etc.). In FIG.3B, a second electrical header 270 is shown with the plate attachmentreversed from the first electrical header 260. Thus, the first (bottom)plate 250 is electrically insulated from header 270 by insulation 290,while the second plate 255 is welded on to header 270 with weld 280.This configuration permits adjacent oppositely charged plates inparallel alignment to promote superior coagulation in the cell 200. Thecurrent sent to each header 260 and 270 is alternated in timed intervalsto avoid the build-up of contaminants at either the anode or cathode. Inthe preferred embodiment, the polarity is alternated typically between 1and 10 minutes.

[0045] The process utilizing the electrochemical cell 200 is ideallysuited for removal of negatively charged suspended solids, includingoils, clays, silt, chlorinated organics, bacteria, microorganisms andmetals such as arsenic, molybdenum or chromium which are coprecipitated.

[0046] An alternative embodiment of the present invention is for waterpurification for potable water. Water purification for potable waterwould not require the steps prior to treatment in the electrochemicalcell 200. The rest of the process and apparatus of this embodiment isthe same as that described above with respect to the first embodiment.

[0047] The process described is also ideally suited for removal ofpositively charges suspended solids such as heavy metals, includingcopper, cadmium, nickel and zinc. This can be particularly useful, forexample, in removing these contaminants from wastewater effluent ofmining operations. In that case, and exemplary of an alternateembodiment of the present invention, polymer is injected into thewastewater prior to the wastewater entering the electrochemical cell200, accompanying the addition of polymer into the wastewater afterexiting the cell 200. This embodiment is depicted in FIG. 1 in dottedoutline. The wastewater leaving strainer 61 is injected with an anionicpolymer at step 63 and compressed air at step 65 in the same manner asdescribed above with respect to steps 52 and 54. The order in which thecompressed air and polymer are injected does not affect the operation ofthe process in any significant manner. The wastewater with the injectedpolymer and compressed air is then passed through an in-line staticmixer 67, which may be identical to the in-line static mixer 23. Thenegatively charged polymer is attracted to the positively chargedmetals, forming negatively charged flocs with the metal ions. Themixture leaving the mixer 67 is then pumped into inlet 210 (FIG. 2) bypump 306 as previously described. Once in the electrochemical cell 200,the negatively charged flocs containing the metal ions are attracted tothe positively charged metal ions released from the plates 250 and 255,forming even larger flocs. The negatively charged particles arecoagulated in the electrochemical cell 200 as described above withrespect to the first embodiment of the present invention, and furthercoagulation of all the flocs occurs upon injection of compressed air atstep 52 and of polymer at step 54. The rest of the process of thisembodiment is the same as that described above with respect to the firstembodiment.

[0048] Having thus described preferred embodiments of a wastewatertreatment system and process for contaminant removal, it will beapparent by those skilled in the art how certain advantages of thepresent invention have been achieved. It should also be appreciated thatvarious modifications, adaptations, and alternative embodiments thereofmay be made within the scope and spirit of the present invention. Forexample, the treatment of industrial wastewater has been illustrated,but it should be apparent that the inventive concepts described abovewould be equally applicable to an endless array of applicationsincluding ground water clean-up, storm water treatment, sewagetreatment, preparation of potable water, mineral processing and miningwater treatment. Moreover, the words used in this specification todescribe the invention and its various embodiments are to be understoodnot only in the sense of their commonly defined meanings, but to includeby special definition in this specification structure, material or actsbeyond the scope of the commonly defined meanings. Thus, if an elementcan be understood in the context of this specification as including morethan one meaning, then its use in a claim must be understood as beinggeneric to all possible meanings supported by the specification and bythe word itself. The definitions of the words or elements of thefollowing claims are, therefore, defined in this specification toinclude not only the combination of elements which are literally setforth, but all equivalent structure, material or acts for performingsubstantially the same function in substantially the same way to obtainsubstantially the same result. The described embodiments are to beconsidered illustrative rather than restrictive. The invention isfurther defined by the following claims.

We claim:
 1. A process for removing contaminants from a wastewaterstream, comprising: feeding said wastewater stream into anelectrochemical cell, wherein electricity is passed through thewastewater stream to produce a coagulated stream; passing saidcoagulated stream, injected with a coagulating reagent, to a mixer,wherein mixing of the coagulated stream with the coagulating reagentproduces a reagent-mixed liquid; and passing said reagent-mixed liquidpast a vent and into a flotation cell.